1. Field of the Invention
The field of the invention is electrical systems and, more particularly, methods and systems for parallel arc detection in electrical systems.
2. Brief Description of Related Art
Electrical systems in residential, commercial, and industrial applications usually include a panel board for receiving electrical power from a utility source. The power is routed through the panel board to one or more current interrupters such as, but not limited to circuit breakers, trip units, and others.
Each current interrupter distributes the power to a designated branch, where each branch supplies one or more loads with the power. The current interrupters are configured to interrupt the power to the particular branch if certain power conditions in that branch reach a predetermined set point. For example, circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high-level short circuit fault condition.
Many such circuit breakers provide this protection through for example a thermal-magnetic trip device. Such a trip device typically includes a bimetal which, in response to the heating effects of a persistent overcurrent condition, deflects to unlatch a trip mechanism, which in turn opens separable contacts of the circuit breaker to interrupt current flow in the protected circuit. In the event of a relatively high-level short circuit fault condition, a magnetic field is created which causes rapid displacement of a magnetic armature in the circuit breaker which in turn drives a nearly instantaneous actuation of the trip mechanism.
Additionally, some current interrupters can interrupt power due to a ground fault, and are commonly known as ground fault current interrupters (GFCIs). The ground fault condition results when an imbalance of current flows between a line conductor and a neutral conductor, which could be caused by a leakage current or an arcing fault to ground.
Other current interrupters can interrupt power due to an arcing fault, and are commonly known as arc fault current interrupters (AFCIs). Typical examples of AFCIs include but are not limited to: arc fault circuit breakers, branch/feeder arc fault circuit interrupters, outlet circuit arc fault circuit interrupters, cord arc fault circuit interrupters, combination arc fault circuit interrupters, which function as either a branch/feeder or an outlet circuit AFCI; and portable arc fault circuit interrupters.
Arcing faults are defined into two main categories, series arcs and parallel arcs. Series arcs can occur, for example, when current passes across a gap in a single conductor. Conversely, parallel arcs can occur when current passes between two conductors of different potential, such as for example, between a power conductor and a ground. The parallel arc can draw currents in excess of normal rated current in a circuit, but with RMS current values are less than that required to produce a thermal trip. Additionally, the arc voltage and line impedance prevent the parallel arc from drawing peak current levels that are high enough to trigger the instantaneous trip function.
Unfortunately, arcing faults may, for various reasons, not cause a conventional circuit interrupter to trip. The potential for fires to occur from arcs increases as homes become older and electrical wiring deteriorates from age.
Accordingly, need exists for current interrupters and methods for detecting parallel arc faults in AC electrical systems that overcome, alleviate, and/or mitigate one or more of the aforementioned and other disadvantages of prior art systems.